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FileSystemWatcher issue

P: n/a
Hi,

I developed a filewatcher service to monitor file creation on a network
drive - 90% time it works fine and from time to time I found out that the
newly created file on that network drive does not trigger the event - all I
have to do is to restart the service.

I kind of suspect the reason is when the target matchine where monitored
drive is on gets rebooted, the filesystemwatcher lost its "monioring"
capability, is that true? if so, how could I detect such event (remote
machine rebooted or unavailable) so I could restart the monitoring when the
target machine is online again?

Thanks very much!
John
Nov 17 '05 #1
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P: n/a
This is an extract of an article I wrote lately
(http://www.utmag.com/wconnect/wc.dll...me~9,7,10,,792) :

After a week that my application was running correctly, it suddenly stopped
without any errors. My application was still running but stopped receiving
events when files where created. After digging, I discovered that the
network connection has cut for about 2 minutes the night before. Since the
cut, no events were raised. This behavior can easily be tested simply by
deleting the root folder you set in the Path property. I had to find a
solution! Here is one I will share with you. You need to do two
modifications to the code above. The first one concerns the Error event
handler. Change the code you have for this event for this new one:

Private Sub FSWError( _
ByVal sender As Object, _
ByVal e As System.IO.ErrorEventArgs)
'Signature to use for the Error event
lstEvents.Items.Add("FSWError detected some activity at " & _
Date.Now.ToString)
lstEvents.Items.Add(" " & e.GetException.ToString)
FileSystemWatcher1.EnableRaisingEvents = False

Do Until FileSystemWatcher1.EnableRaisingEvents
Application.DoEvents()
Try
InitFSW()
FileSystemWatcher1.EnableRaisingEvents = True
lstEvents.Items.Add(" Now back to work!!! " & _
Date.Now.ToString)
Catch ex As Exception
FileSystemWatcher1.EnableRaisingEvents = False
lstEvents.Items.Add(" Still have problems with the folder at "
& _
Date.Now.ToString)
Threading.Thread.Sleep(5000)
End Try
Loop
End Sub
When the folder is deleted (or when the network connection gets cut), an
error is raised and the FileSystemWatcher object gets corrupted. This code
simply tries to reset the FileSystemWatcher properties and to re-enable it.
If this succeeds, it means that everything is back to normal.
I have said 2 modifications. This second modification is that you need to
remove the handler to the events when you recreate the FileSystemWatcher
object. You need to add these lines to the InitFSW method before setting the
Path property:

'Remove handlers of the previous instance
RemoveHandler .Changed, AddressOf FSWHandler1
RemoveHandler .Created, AddressOf FSWHandler1
RemoveHandler .Deleted, AddressOf FSWHandler1
RemoveHandler .Renamed, AddressOf FSWHandlerRename
RemoveHandler .Error, AddressOf FSWError
If you don't remove the handlers and your FileSystemWatcher has errors and
is recreated, you will receive one event for every time the AddHandler has
been executed.

--
HTH

Éric Moreau, MCSD, Visual Developer - Visual Basic MVP
(http://aspnet2.com/mvp.ashx?EricMoreau)
Conseiller Principal / Senior Consultant
Concept S2i inc. (www.s2i.com)

"John Lee" <jo***@newsgroup.nospam> wrote in message
news:eR**************@TK2MSFTNGP15.phx.gbl...
Hi,

I developed a filewatcher service to monitor file creation on a network
drive - 90% time it works fine and from time to time I found out that the
newly created file on that network drive does not trigger the event - all
I have to do is to restart the service.

I kind of suspect the reason is when the target matchine where monitored
drive is on gets rebooted, the filesystemwatcher lost its "monioring"
capability, is that true? if so, how could I detect such event (remote
machine rebooted or unavailable) so I could restart the monitoring when
the target machine is online again?

Thanks very much!
John

Nov 17 '05 #2

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